1. Field of Invention
The present invention relates to a liquid crystal (LC) alignment agent, a LC alignment film and a LC display (LCD) device having thereof. More particularly, the present invention relates to a LC alignment agent having better voltage holding ratio (VHR) and process stability, a LC alignment film and a LCD device having thereof.
2. Description of Related Art
At present, the polymers such as polyamide acid, polyimide, and the like, are used as a liquid crystal alignment agent, after coating onto a substrate having a transparent conducting film, heating and alignment process to form a liquid crystal alignment film for the liquid crystal display element. Finally, two of the substrates coated with alignment film are placed in opposite directions to form a LCD device holding a liquid crystal layer between the two substrates.
However, the liquid crystal alignment films of the prior art have inferior rubbing resistance, which results in poor pretilt angle stability. Hence, in order to improve the abrade phenomenon of alignment films, epoxy compounds are added to the alignment agent, such as Japanese Patent Publication No. 07-234410 and Japanese Patent Laid-Open No. 2006-23334. However, unreacted epoxy compounds easily remain in such LC alignment film after post-bake treatment, resulting in some shortcomings of worse voltage holding ratio (VHR) and process instability of the LCD device.
Accordingly, it is necessary to provide an LC alignment agent for improving shortcomings of worse voltage holding ratio (VHR) and process instability of the prior LCD device due to the residual of unreacted epoxy compounds after coating and post-bake treatments.